Hot shower issues in a small hotel

[DrMince]

We recently acquired a small hotel in the sticks.

We (and our guests) have noticed that it is difficult to get the electric showers to produce enough hot water for a comfortable shower, even on fairly warm days.

 

The local shower/aircon maintenance team say that the units are not the problem but that the power supply is the problem.

 

There are multiple power lines coming in off the street to the various buildings we have at the hotel. For now I want to understand the problem, and the fix, in our house before implementing the fix to the guest rooms.

 

I know nothing about electricity but I will list here what I have seen by looking around the hotel grounds and doing a simple test in the house.

 

1. The cables running from the street to our house are about 80m long.

2. The cables are old and covered in squirrel nibbles, sometimes to the aluminium.

3. They appear to be 10 Sq mm PVC 750v 70c.

4. The shower units are 3.5KW new devices (two units).

5. I have plugged in a UPS with a voltage display to see is coming through the sockets.

 

With just the fridge and computer on, the UPS is showing about 205v input.

With one shower turned on it goes down to 185v input.

With both showers on it goes down to 165v input.

 

I have no idea if this is normal or if it is the problem.

Please let me know if you need any further information before coming up with suggestions.  

 

Thanks for any help you can give.

[Momofarang]

Normal... by Thai standards.

 

Look at your meter calibration and divide the numbers by the product of (local corruption level) by (130-Local average IQ).

[Crossy]

First, get yourself a cheap multimeter, rather more portable than using your UPS ????

 

Check the voltage at the meter both off load (turn off the main breaker) and with one, then two showers (it's the voltage here that the supply authority will be interest in).

 

What size meter do you have (5/15, 15/45, 30/100)?

 

80m of 10mm² Al is certainly going to do something significant to your supply voltage, but's let's start at the incoming mains.

 

It's worth noting that at 165V your 3.5kW showers will actually be producing about 2kW which at this time of year will be producing a lukewarm dribble ????

 

 

 

 

[Crossy]

For comparison purposes this is our supply voltage vs current graph. Note that the starting voltage (at about 8A) varies with day and time of day. Even so we're still "reasonable" at 50A. Measurements were taken in 2017.

 

[xylophone]

Judging by your post and the voltage measurements, I would say that the voltage is far too low to be able to heat the water effectively.

 

The fact that the voltage drops quite markedly from 205 V (even though that is low) to 185 V and then down to 165 V suggests a couple of possibles............. the cable is not up to the job, even though from a rough check I have done, it should be able to handle about 60 A load or thereabouts and unless there are some other hefty devices in the circuits, that should be okay.

 

Adding more load to older circuits/cables will often shows up poor connections/faulty connections and if the connections are poor/faulty, then not only will you get a voltage drop, you could quite possibly get a fire.

 

Time to get a farang electrician in I would think.

[VocalNeal]

I'm thinking you go to the local EGAT/PEA office where the orange trucks are and speak to a foreman and get someone to explain about the 80m. They might be persuaded to run a new supply, if that is the problem, using some (cough) spare cable. 

[Crossy]

Good advice above.

 

BUT.

 

If you are going to go to PEA you need to be armed with FACTS. If you have low voltage at the meter that's their problem which they should sort.

 

They could easily move you to a less loaded phase which may solve your issues. Cost - lunch for the boys who sort it. 

 

You will indeed likely be replacing your incoming cable, but if you can get away without why spend your hard earned $$?

 

[OneMoreFarang]

You should solve this problem ASAP.

Please look up Brownout and the bad thigs which might happen.

 

Here is some info:

https://superuser.com/questions/113113/why-are-brownouts-so-harmful

 

[wayned]

5 hours ago, Crossy said:

Good advice above.

 

BUT.

 

If you are going to go to PEA you need to be armed with FACTS. If you have low voltage at the meter that's their problem which they should sort.

 

They could easily move you to a less loaded phase which may solve your issues. Cost - lunch for the boys who sort it. 

 

You will indeed likely be replacing your incoming cable, but if you can get away without why spend your hard earned $$?

 

If you go to PEA you need to be armed with something in addition to facts.  You need someone that understands the problem and speaks fluent Thai.  Go ing to PEA or TOT where I live is a real problem unless you speak Thai.

[DrMince]

Thanks everyone for the advice received so far.

I noticed in the early hours of this morning that my UPS was recording 245v of input.

 

I will buy a multimeter today and collect a lot more data to better understand the problem. I will publish my findings here again in a week or two.

 

p.s. The meter is 15/45.

[jackdd]

What is the outside temperature at your place, especially in the night, if we are talking about taking a shower in the morning.

3500w is just underpowered if it gets a bit cooler.

 

We have 4800w here (living in Chiang Mai, currently down to about 17 degrees in the night), and if i want to take a warm shower in the morning i can not fully open the water tap in the shower.

A week or two ago when it was like 10 degrees here in the night, when i wanted to take a warm shower in the morning i could open the water tap only at the absolute minimum (so that the water heater was active, if the flow is too low it shuts off), and this was still far from hot.

 

So even if your voltages are ok, you might need to get at least a 6000w unit to be able to take a proper warm shower all year round.

 

[mogandave]

I’m surprised mor people don’t use boilers here, particularly people that use a lot of hot water.

[wayned]

1 hour ago, mogandave said:

I’m surprised mor people don’t use boilers here, particularly people that use a lot of hot water.

When I built my house 22 years ago I wanted to plumb it like a house in the USA with hot and cold water everywhere.  I looked for a "boiler", a 30 gallon glass lined gas water heater and was unable to locate one anywhere.  All that I could find was big industrial/comercial units units at a  large industrial/commercial cost.

[Metropolitian]

On 12/19/2019 at 11:42 PM, wayned said:

When I built my house 22 years ago I wanted to plumb it like a house in the USA with hot and cold water everywhere.  I looked for a "boiler", a 30 gallon glass lined gas water heater and was unable to locate one anywhere.  All that I could find was big industrial/comercial units units at a  large industrial/commercial cost.

Did the same quest. Was looking for a second hand insulated enclosure. An old boiler would then do. The aim was putting a heat exchanger inside connected to a coil on the rooftop. Free warm water, for the laundry, dishes and mixer in the shower.

The quest is still on

[CGW]

On 12/18/2019 at 3:56 PM, jackdd said:

So even if your voltages are ok, you might need to get at least a 6000w unit to be able to take a proper warm shower all year round.

It's the same where I am, water just gets too cold for the heater! we have a 8,000w heater, couple of weeks back when it was "cold" difficult at best to get a 'hot" shower!

[Fruit Trader]

11 minutes ago, CGW said:

It's the same where I am, water just gets too cold for the heater! we have a 8,000w heater, couple of weeks back when it was "cold" difficult at best to get a 'hot" shower!

These 30kW jobs overcome the cold water issues and are slowly becoming more popular. Good for washing the dishes too.

 

 

 

[VocalNeal]

On 12/18/2019 at 3:56 PM, jackdd said:

What is the outside temperature at your place, especially in the night, if we are talking about taking a shower in the morning.

3500w is just underpowered if it gets a bit cooler.

 

We have 4800w here (living in Chiang Mai, currently down to about 17 degrees in the night), and if i want to take a warm shower in the morning i can not fully open the water tap in the shower.

A week or two ago when it was like 10 degrees here in the night, when i wanted to take a warm shower in the morning i could open the water tap only at the absolute minimum (so that the water heater was active, if the flow is too low it shuts off), and this was still far from hot.

 

So even if your voltages are ok, you might need to get at least a 6000w unit to be able to take a proper warm shower all year round.

 

4-ish Kw is OK in Bangkok or further south. Up north you need 5-6.5 min. Incoming water is colder

[mogandave]

On 12/19/2019 at 11:42 PM, wayned said:

When I built my house 22 years ago I wanted to plumb it like a house in the USA with hot and cold water everywhere.  I looked for a "boiler", a 30 gallon glass lined gas water heater and was unable to locate one anywhere.  All that I could find was big industrial/comercial units units at a  large industrial/commercial cost.

I couldn’t find anything when I moved here, so I brought two Rheem 50 gallon electric units from the US, still have one, both still working as far as I know. 
 

That said, they are becoming more popular and Homepro seems to have fair prices on what looks like decent product:

 

 

[keithkarmann]

Just bought a gas heater from Lazada for 1100 baht. I already have two very similar gas heaters , one for the house and one for the outside jacuzzi bath. They have adjustments for Summer/Winter and during the recent cold spell they were struggling to supply decent hot water until I turned up the controls for Winter conditions and they gave me 40c plus with water going in at below 15c. When I built my house I did not want large electric cables supplying electric heaters that could not cope. Not sure how good the new 1100 baht heater will be but these heaters can be bought for more but this new one looks the same as the heater I paid 5000 baht for (still working) 7 years ago. Electric shower heaters have a limited life and you can't get a shock off a gas heater. 

[maxisrael]

We have good quality gas heaters installed (not inside ! ) and even when it is very cold like 10 degrees C we still have good warm water access and the water in our holding tanks are cold as well we have our own water source here in a rural area. 

[millymoopoo]

Yes, voltage drop is the problem.

Replacing the 80m run of cable to you with 150amp rated cable would be a good start, but expensive.

And replace them with copper not aluminium as copper has less voltage drop.

There's not much else you can do other than restrict the flow of water through the heater so what does flow through has more chance of heating up.

[emptypockets]

Do a maximum demand calc and size the incomer for 5%voltage drop.

I've assumed the problem is not the supply authorities.

Get that checked first, as stated in other posts it may be the cheapest solution.

[Tbone999]

If you check out this page and add in your values, https://www.rapidtables.com/calc/wire/voltage-drop-calculator.html then there should in reality be little voltage drop across that length of cable. To see that at a starting voltage of 205V (which is pretty bad) for it to drop 20V when turning on one unit (3500W = 17A @ 205V), would lead me to believe that you have a bad connection on the incoming supply somewhere, unless the main supply in is really bad, but I can't see your house taking down the main PEA supply over a heater unit!! I would get in a competent electrician to go over your place and check out the wiring. Don't forget, when the incoming supply goes down, the current draw on all your household devices goes up, which stresses all the components, also any poor connection areas will heat up causing a fire hazard. But as also advised, I would be taking down the multimeter readings every couple of hours and record them for any assistance you might need from PEA for changing out the line anyway as it sounds to be in bad condition. (BTW, the bad connection could also be where the incoming 80m line is connected to the main PEA line), so you might need there assistance anyway, which  you could ask the electrician to liaise with PEA if he discovers that is the case.

[Tbone999]

8 minutes ago, Tbone999 said:

If you check out this page and add in your values, https://www.rapidtables.com/calc/wire/voltage-drop-calculator.html then there should in reality be little voltage drop across that length of cable. To see that at a starting voltage of 205V (which is pretty bad) for it to drop 20V when turning on one unit (3500W = 17A @ 205V), would lead me to believe that you have a bad connection on the incoming supply somewhere, unless the main supply in is really bad, but I can't see your house taking down the main PEA supply over a heater unit!! I would get in a competent electrician to go over your place and check out the wiring. Don't forget, when the incoming supply goes down, the current draw on all your household devices goes up, which stresses all the components, also any poor connection areas will heat up causing a fire hazard. But as also advised, I would be taking down the multimeter readings every couple of hours and record them for any assistance you might need from PEA for changing out the line anyway as it sounds to be in bad condition. (BTW, the bad connection could also be where the incoming 80m line is connected to the main PEA line), so you might need there assistance anyway, which  you could ask the electrician to liaise with PEA if he discovers that is the case.

By the way, this is a separate issue from why your unit isn't producing enough hot water, it's probably due to not being powerful enough for your area, but fixing the input supply first then go from there.

[Burma Bill]

I also live out in the sticks and I have the same problem. In my case it is NOT the power supply, but being on mains water supply from PWA, it is the WATER PRESSURE. My shower unit has a safety switch which disables the heat supply to avoid scolding water. Low pressure = no warm water, only cold! As I type, our local water supply is shut, so at this moment no water at all! This always happens in the dry season here in Issan when mains water supply is rationed/restricted from the reservoirs. I keep large plastic containers filled with water in reserve.

[Matzzon]

On 12/17/2019 at 11:31 AM, DrMince said:

165v

That´s a problem!

[emptypockets]

3 hours ago, Tbone999 said:

If you check out this page and add in your values, https://www.rapidtables.com/calc/wire/voltage-drop-calculator.html then there should in reality be little voltage drop across that length of cable. To see that at a starting voltage of 205V (which is pretty bad) for it to drop 20V when turning on one unit (3500W = 17A @ 205V), would lead me to believe that you have a bad connection on the incoming supply somewhere, unless the main supply in is really bad, but I can't see your house taking down the main PEA supply over a heater unit!! I would get in a competent electrician to go over your place and check out the wiring. Don't forget, when the incoming supply goes down, the current draw on all your household devices goes up, which stresses all the components, also any poor connection areas will heat up causing a fire hazard. But as also advised, I would be taking down the multimeter readings every couple of hours and record them for any assistance you might need from PEA for changing out the line anyway as it sounds to be in bad condition. (BTW, the bad connection could also be where the incoming 80m line is connected to the main PEA line), so you might need there assistance anyway, which  you could ask the electrician to liaise with PEA if he discovers that is the case.

Agree with the potential bad connection, especially with AL conductors. Not so sure about increased current flow due to low voltage though in an inductive load like a heater, unless Ohms law has changed. Low frequency yes but I suspect that is not the issue here.

Simple check would be to check the voltage at the meter and at the point of connection. Then turn on both heaters and see if the voltages at both points change significantly. If it drops at the meter then it will be either the PEA's problem or a very bad connection at his incoming mains/meter connection. If the voltage remains constant at the meter after turning on the heaters and drops at the point of connection (i.e his CU) then he has a cable problem. Ohms law to the rescue again.

[Autonuaq]

The equipment is made for a range of 230 V~ plus or minus 10% 50Hz

For most countries.

 

Some have still 110 V~ with 60 Hz.

 

In this range it works and keeps operating as designed by the specs.

 

You seem to have a to low input of voltage (V) and when you ask more electricity then the current (A) increase while the Voltage drops.

 

The power available use to heat the water is voltage x current (V×A)

Since the power drop the total heating power drops

 

Thism kaes that the water is feeling colder then expected

 

To increase the heat transfer to the water you can reduce the water thruput flow.

Lesser water to heat the quicker the water can raise its temperature.

 

Negative effect you get a very small water flow from the shower. Making the showering sensation lesser for most people.

 

The power delivered to your location is the problem this has to do with the overloading of the grid in your area. This is a major problem in many areas and can only be solved by installing more powerlines, and or upgrade the transformer you have at the hotel.

The easiest way is to check the transformer if thattransformer is well balanced for the property.

Then if that is correct you have to measure the input of the transformer for about 4 weeks. Then you have a solid case to complay with good underlaying documents.

[sometimewoodworker]

3 hours ago, Burma Bill said:

I also live out in the sticks and I have the same problem. In my case it is NOT the power supply, but being on mains water supply from PWA, it is the WATER PRESSURE. My shower unit has a safety switch which disables the heat supply to avoid scolding water. Low pressure = no warm water, only cold! As I type, our local water supply is shut, so at this moment no water at all! This always happens in the dry season here in Issan when mains water supply is rationed/restricted from the reservoirs. I keep large plastic containers filled with water in reserve.

This is why many/most people around here have water tanks as we do.
 

For us we can go about 6~10 weeks on full usage with hot showers, and about 10 days with no power while still having (all be it cold/cool) showers and washing up, toilet water

[Pdavies99]

5 hours ago, Burma Bill said:

I also live out in the sticks and I have the same problem. In my case it is NOT the power supply, but being on mains water supply from PWA, it is the WATER PRESSURE. My shower unit has a safety switch which disables the heat supply to avoid scolding water. Low pressure = no warm water, only cold! As I type, our local water supply is shut, so at this moment no water at all! This always happens in the dry season here in Issan when mains water supply is rationed/restricted from the reservoirs. I keep large plastic containers filled with water in reserve.

 Just buy a water tank and pump? Problem ref water finished!