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Problem With Boiler Replacement

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joben1

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Hi All,

I have a thermal store central heating system which has 2 pumps, one for hot water and one for central heating. My boiler has been replaced and I know they had trouble with the wiring. They told me that one of the pumps wasn't calling for heat but now all is ok. However, I have found that both the hot water and central heating are using just one of the pumps. I called them and they told me that it seems that modern boilers don't work with 2 pump systems, and the solution is to remove one of the pumps and fit a valve that diverts the flow of water depending on what's calling for heat (presumably a Y plan 3 port valve that allows both to call for heat?).

This doesn't sound right to me. Surely there are boilers that would work with my system? Are they pulling a fast one? Any advice would be much appreciated.
 
Last edited:
joben1 said:
Hi All,

I have a thermal store central heating system which has 2 pumps, one for hot water and one for central heating. My boiler has been replaced and I know they had trouble with the wiring. They told me that one of the pumps wasn't calling for heat but now all is ok. However, I have found that both the hot water and central heating are using just one of the pumps. I called them and they told me that it seems that modern boilers don't work with 2 pump systems, and the solution is to remove one of the pumps and fit a valve that diverts the flow of water depending on what's calling for heat (presumably a Y plan 3 port valve that allows both to call for heat?).

This doesn't sound right to me. Surely there are boilers that would work with my system? Are they pulling a fast one? Any advice would be much appreciated.
Click to expand...
What tosh, it sound like they don't know what they are talking about.
What is the make / model of thermal store & the boiler?
Sounds like boiler heats thermal store via a pump, another pump on store is controlled by time clock & room stat which draws water from the sore to provide heating & thermal store looks after the hot water which is instantaneous.
 
No it isn't working. Only one of the pumps is being used.

How it works is that one of the pumps is for the hot water, and one for central heating, but now both the hot water and central heating are using just one of the pumps. I'm not sure which pump is being used, but when I run both hot water and central heating, the radiators get so hot it gets uncomfortable no matter how I set the room thermostat. This leads me to believe that the central heating pump is the one being used.
 
chris watkins said:
What tosh, it sound like they don't know what they are talking about.
What is the make / model of thermal store & the boiler?
Sounds like boiler heats thermal store via a pump, another pump on store is controlled by time clock & room stat which draws water from the sore to provide heating & thermal store looks after the hot water which is instantaneous.
Click to expand...

The store is an Albion Mainsflow and the new boiler is a Worcester Ri ErP+.
 
Hot water isn't instantaneous. It's controlled by a thermostat on the store and the hot water pump draws the water through the boiler. Unless I've misunderstood you.
 
not sure how they could make this system work with only one pump. the hot water pump as you call it in effect supplies both hot water and heating when you demand both as it heats the store water then the heating pump takes the water out of the store to heat the radiators. With thermal stores you have to usually run the boiler on maximum as the store thermostat will be set to about 75c so if you run the boiler too low it will never turn off unless you use the timer to turn it off. One of the side effects of having the new boiler fitted is it is much more capable of maintaining this high temperature across the whole system resulting in much higher rad temps than you are used to. one way to check pump operation is to run hot water on its own and only the store pump should run. turn off the hot water if you have a timer and run heating on its own. heating pump should run but boiler shouldnt fire and store pump shouldnt run. looked at wiring diagrams and cant see any interlock between hw and ch operation that wont let you try this
 
These are old pictures of the original store in the process of bring replaced like for like.

DSC01141_zpsfa20d41a.JPG


DSC01142_zps5388415a.JPG
 
joben1 said:
Hot water isn't instantaneous. It's controlled by a thermostat on the store and the hot water pump draws the water through the boiler. Unless I've misunderstood you.
Click to expand...
The hot water will be instantaneous so long as the store is up to temperature. There is not stored domestic HW only primary heating water when a hot tap is turned on the mains cold water is heated instantaneously.
 
garygvl said:
not sure how they could make this system work with only one pump. the hot water pump as you call it in effect supplies both hot water and heating when you demand both as it heats the store water then the heating pump takes the water out of the store to heat the radiators. With thermal stores you have to usually run the boiler on maximum as the store thermostat will be set to about 75c so if you run the boiler too low it will never turn off unless you use the timer to turn it off. One of the side effects of having the new boiler fitted is it is much more capable of maintaining this high temperature across the whole system resulting in much higher rad temps than you are used to. one way to check pump operation is to run hot water on its own and only the store pump should run. turn off the hot water if you have a timer and run heating on its own. heating pump should run but boiler shouldnt fire and store pump shouldnt run. looked at wiring diagrams and cant see any interlock between hw and ch operation that wont let you try this
Click to expand...

Yes the boiler has to be set to maximum. My description of how it works is a laymans description. I have had electrical engineering training but never been a plumber so have had to try and work out how it works in my head.

I tested it by setting both stats to min, turning on central heating and hot water, one at a time, and turning up the relevant stat. The boiler fires up in both cases but they both use the same pump (tested by feeling the pumps).
 
chris watkins said:
The hot water will be instantaneous so long as the store is up to temperature. There is not stored domestic HW only primary heating water when a hot tap is turned on the mains cold water is heated instantaneously.
Click to expand...

As I understand it, the domestic hot water is mains water combined with store water through a thermostatic mixer valve.

Screenshot.png
 

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