Changing heater size

TXWill

New member
Apr 8, 2020
4
Rockwall Texas
I have a 9000 gallon small pool that had a MasterTemp 400 heater installed. The basket and coils rusted out and the replacement parts are not worth investing in a 9 year old heater.

I was thinking about a new MasterTemp 250 bc it is a bit less expensive and the hookups should be easy except for the different pipe sizes.
Any concerns about going from the 400 to the 250? Thoughts? Suggestions?

thanks all!
 

HermanTX

Gold Supporter
May 20, 2020
774
Katy TX
Couple of points to consider.
If the pipe size is different then the flowrate thru heater is different. Thus this will affect how fast you can raise the temperature. Each heater has a heating chart so best to research that and ensure that meets your expectations with the smaller heater.
You should have sufficient gas supply as the 400 takes more gas flowrate. May want to verify if you need to reduce the gas flowrate for the smaller heater. that can be done by the installer.
Hope this helps.
 

TXWill

New member
Apr 8, 2020
4
Rockwall Texas
These are both good points. You are right, I think the MT400 does have larger pipes than the MT250. Is that a “problem” or just something I will have to re-plumb?
Will

Couple of points to consider.
  • If the pipe size is different then the flowrate thru heater is different.
  • May want to verify if you need to reduce the gas flowrate for the smaller heater.
 

HermanTX

Gold Supporter
May 20, 2020
774
Katy TX
These are both good points. You are right, I think the MT400 does have larger pipes than the MT250. Is that a “problem” or just something I will have to re-plumb?
Will
I did not research the external inlet and outlet connections but if the connections on the MT250 are different from the MT400 you may need to use a reducer or adapter. That should not be a major issue for the installer. What is more important is that the MT250 has less BTUs so it will not heat the water as quickly. I looked at a brochure and it showed a 400 unit will take 44 minutes for a 30deg temp rise whereas a 250 unit will take 78 mins. for a 1000 gals spa. So your expectations for how fast the pool will heat will need to consider the longer time frame.
 

TXWill

New member
Apr 8, 2020
4
Rockwall Texas
yeah, I guess I will have to accept the slower warmup time for the lesser price. It’s a super small 9000 gallon pool so I’m thinking it will be ok. I will prob be the installer, I removed the MT400 and rerouted the pluming to bypass the heater for now, but thinking hooking up the 250 in its place will be relatively easy.