Water Pressure problem

[Mango Bob]

I have a Mitsubishi Water Pump EP-155Q2. My problem is when I take a shower and want hot water I need to turn the water down so i get a flow of hot water, this causes the water pressure to first drop and come back up again and drop and come back up again. To solve my problem I turn on the water in my sink while I take a shower to keep the pressure up. Doesn't anyone know the solution to my problem? I hate to waste water especially at these times in Thailand.

[h90]

it is a "problem" of the pressure switch. Actually a good thing normally as else the pump would turn on/turn off much more often.

I don't know if it is adjustable on your switch.

[kannot]

dont forget it will depend on the size of your shower unit ie kw rating as to "how fast" it can heat the water going thru it also

[RichCor]

Your pump is probably short-cycling due to the smaller reserve pressure vessel of the EP-155Q2 vs the built-in bladder tank on the WP- series.

When the water flows at an odd rate the pump fills the small pressure tank too quickly, then short-cycling (on/off/on/off) while it tries to maintain water pressure.

You might want to look into installing a larger reserve pressure tank that will maintain line flow rate and pressure so the pump doesn't get overworked short-cycling.

[RichCor]

All water heaters will have a sweet-spot for input temp vs output temp at (L/m) a certain water flow.

Some people like high L/m water flow so will need high-wattage heaters, sometimes needing 3-Phase power to do a proper job.

Otherwise, lowering the flow rate will allow for higher output temperatures.

[sometimewoodworker]

Your pump is probably short-cycling due to the smaller reserve pressure vessel of the EP-155Q2 vs the built-in bladder tank on the WP- series.

When the water flows at an odd rate the pump fills the small pressure tank too quickly, then short-cycling (on/off/on/off) while it tries to maintain water pressure.

You might want to look into installing a larger reserve pressure tank that will maintain line flow rate and pressure so the pump doesn't get overworked short-cycling.

The EP series are constant pressure and designed for use with showers

The WP series are designed as well pumps and Mitsubishi does not recommend them for use with electric showers.

A separate pressure tank may help the built in accumulator as you clearly need a lower flow rate than your pump is happy with.

Edited September 20, 2015 by sometimewoodworker

[RichCor]

Your pump is probably short-cycling due to the smaller reserve pressure vessel of the EP-155Q2 vs the built-in bladder tank on the WP- series.

When the water flows at an odd rate the pump fills the small pressure tank too quickly, then short-cycling (on/off/on/off) while it tries to maintain water pressure.

You might want to look into installing a larger reserve pressure tank that will maintain line flow rate and pressure so the pump doesn't get overworked short-cycling.

<...>

The EP series are constant pressure and designed for use with showers

The WP series are designed as well pumps and Mitsubishi does not recommend them for use with electric showers.

A separate pressure tank may help the built in accumulator as you clearly need a lower flow rate than your pump is happy with.

It would be interesting to know where you found the bit about "Mitsubishi does not recommend them for use with electric showers."

Did they give a reason?

If an EP-series pump was attached to a gravity-feed water tank to provide flow and pressure, I wonder what the min/max flow rates are, and what they recommend to allow when lower L/m flow rates are desired.

Also, for the OP, an oldie but a goody:

Question For Those With Mitsubishi Ep Series Home Water Pumps (archived topic)

Started by Pib, 2010-09-26 11:20

This discusses a similar topic issue.

Though, the poster here solved their WP-series pulse issue by draining water and allowing their pressure tank air reserve to 'recharge'.

[sometimewoodworker]

It would be interesting to know where you found the bit about "Mitsubishi does not recommend them for use with electric showers."

Did they give a reason?

If an EP-series pump was attached to a gravity-feed water tank to provide flow and pressure, I wonder what the min/max flow rates are, and what they recommend to allow when lower L/m flow rates are desired.

From Mitsubishi.

If you want the information in English then Mitsubishi Malasia has it.

As I said the do recommend the EP series for instant showers. They do not recommend the WP series for them.

They also have charts in English that may well answer your other question.

Or you can phone Mitsubishi Thailand and ask, they are helpful and have a few English speaking staff.

DAGS it works I did.

Edited September 20, 2015 by sometimewoodworker

[Pib]

Mitsubishi Malaysia say EP series are suitable for shows, but they don't for the WP series. But I expect they only say that to get you to buy a higher priced EP/CP model versus the WP model and to minimize any pressure variations a person might feel with a "small-sized/low pressure" WP pump like a WP-155 and lower wattage. I use a Mitsubishi WP-255 in my house and it works just fine for showers...I don't feel any pressure variations with my water heater shower.

Mitsubishi Malaysia

http://mitsubishielectricmalaysia.com/index.php/product/water-pump/qs-series/

The problem I was having with my WP-255 back in late 2010 was caused by a "defective air control/balance valve" which keeps the pressure tank from getting waterlogged...keeps just the right amount of air in it to act as an energy spring/air cushion. When a pump such as the ones we are talking about gets waterlogged it will cause the pump to run almost continuously or cause it to frequently cycle on and off very frequently (like every second) which cause the water to pulsate due to no air pressure in the pressure tank...makes it feel like you have a pulsating shower head. Anyway, air control valve replaced (it had a pin hole size rupture in it's rubber diaphragm part)...been good to go ever since.

If the OP's EP series has the small 1 to 2 liter pressure bottle on it sounds like the rubber bladder in it has ruptured which means it will not work any more...it would cause the pump to turn on briefly even with a small leak some where in the system and you would wonder why is the pump turning on as I'm not using any water...and it would cause variation in water pressure.

These small pressure bottles use a rubber bladder inside of them to keep the water and air/nitrogen separated so the air/nitrogen does not naturally get absorbed into the water....they don't need an air balance control value like the WP series needs since the WP series uses a larger pressure tank "without bladder." So, without the rubber bladder some air slowly and naturally gets absorbed into the water causing loss of air pressure in the tank...this is where the air balance control valve comes into play to automatically replace that loss air/keep the air charge correct in the pressure tank.

Edited September 20, 2015 by Pib

[sometimewoodworker]

Mitsubishi Malaysia say EP series are suitable for shows, but they don't for the WP series. But I expect they only say that to get you to buy a higher priced EP/CP model versus the WP model and to minimize any pressure variations a person might feel with a "small-sized/low pressure" WP pump like a WP-155 and lower wattage. I use a Mitsubishi WP-255 in my house and it works just fine for showers...I don't feel any pressure variations with my water heater shower.

You are so correct NOT

directshop. Mitsubishi EP-305QS 7,190 THB vs Mitsubishi WP-305QS 7,100 THB

so they are pushing you to pay an extra 90THB

They are designed for different jobs. the prices are virtually the same

[Pib]

Generally the constant pressure pumps cost more than the non-constant pressure (not to imply you really feel any pressure change in most cases) due to the constant pressure mechanism/electronics they have in them. A person can see that when going into a hardware store where they have many models of the different pump designs and size and compare the prices.

The "tank" type pumps...the type where the motor/manifold assembly sets on top of a small pressure tank work just fine for home use...in fact in my large mooban when I walk around the moobaan with the dogs its pretty easy to see what type of pump people have...the great majority have the non-constant pump/tank type pump like I do. I expect the lower price and the fact they work fine for home use it the reason for that.

Just for a technical/spec comparison of constant pressure and non-constant pressure/tank pumps below is a comparison table of 4 pumps from a Hitachi pump web site comparing the specs between some common sized constant pressure and non-constant pressure/tank pumps....two 250W pumps of each design and two 300W pumps of each design...when looking at the core specs only small differences exist.

[Mango Bob]

Everyone seems to want to out do the other here but no one has helped me solved my problem. What the hell can I do to stop it.

[Pib]

Everyone seems to want to out do the other here but no one has helped me solved my problem. What the hell can I do to stop it.

You've been given several possible problems and fixes/recommendations. Have you tried any of them yet?

[RichCor]

Everyone seems to want to out do the other here but no one has helped me solved my problem. What the hell can I do to stop it.

You've been given several possible problems and fixes/recommendations. Have you tried any of them yet?

Advice offered within thread so far:

Speculated Cause: Your EP-Series 'constant pressure' water pump is either not set or not designed to service lower Liters/minute water flow rate, or it requires maintenance to restore that function. What is your water pump's operating range, compared to the flow rate of your shower heater, as one would think a 'shower' should be within the home water pump's operating range.

1. Perform Maintenance

   Make sure your water pump is running optimally. Verify the built-in accumulator isn't water-clogged, or its bladder require replacement. Do the procedures to 'recharge' the air-pressure in the accumulator. Check the pressure switch settings.

   If it functioned well before then it should do so again with a bit of maintenance or system evaluation.

2. Add a passive "pressure tank"

   A low water-flow requirement can be an issue for constant flow pumps set to deliver higher L/min. Adding an additional pressure tank to the line will allow lower L/m water flow rates to be served without overworking the water pump.

In a linked archived topic one member solved the issue by replacing their EP/WP-Series water pump with an IP-Series "Inverter Pump" that's designed to function effectively with a wider range L/min water flow rates. (Real constant pressure provided by variable speed control inverter circuit)

[maxisrael]

Everyone seems to want to out do the other here but no one has helped me solved my problem. What the hell can I do to stop it.

Buy an inverter pump Mitshubishi iMCH-55 VS or 100 VS

[Thorgal]

If pump goes on/off with only cold water, the pressure switch or bladder tank needs to be checked.

If pump goes on/of with hot water mixture throug water heater, means that your water heater tubing is too small to build constant pressure and that's making your pressure switch tripping of your pump.

Depending on the water heater model you have, you have to check the specs of pump pressure and the specs of your water heater.

Moreover, if you have an electronic controlled water heater, your thermostat will operate a flow regulating (tempering) switch close to the pressure switch limit of your pump. Here again, tripping is possible in combination with small tubing issue. Puting/setting your temperature on lowest level, can give you an indication of proper balance of pump supply and output temperature flow.

See picture at 'constant temperature output' :

http://www.stiebel-eltron-usa.com/products/dhc-e-point-use-tankless-electric-water-heaters

Electric (non-electronic) water heaters have in some cases a manual flow adjusting screw :

Edited February 20, 2016 by Thorgal